Child protection experts in the UK are being consulted as part of the expanding investigation into the operation of a suspected Irish paedophile ring.

Ireland's child protection agency, Tusla, and gardaí are being supported by UK child protection experts who have helped deal with some of the most shocking exploitation cases in England and Scotland over recent years.

The move came as one source warned the investigation is dealing with what is suspected to be the biggest paedophile ring ever uncovered in Ireland.

One source revealed that what the investigation has already uncovered is "truly shocking".

"We are talking about a level of child abuse and exploitation that is more accurately referred to as torture," they said.

Eleven people - five men and six women - were arrested but subsequently released without charge last week.

All were questioned about the alleged abuse and sexual exploitation of children.

A file is now being prepared in relation to the Garda investigation for the Director of Public Prosecution.

The scale and nature of the matters under investigation are so serious that both Justice Minister Charlie Flanagan and Children's Minister Katherine Zappone have been briefed.